Manafort was working on the op-ed, written in English, as recently as Nov. 30. It related to his political work in Ukraine and his foreign lobbying and money laundering criminal charges.

In a court filing, Mueller's team claims "Manafort worked on the draft with a long-time Russian colleague of Manafort's, who is currently based in Russia and assessed to have ties to a Russian intelligence service," ABC News reported.

The filing from Mueller's team Monday asked the court to renegotiate the $10 million unsecured bail and house arrest agreement Mueller's office and Manafort's lawyers made last week. It asserts the op-ed reflects "an intention to violate or circumvent the Court's existing Orders." Therefore, "the government submits that the proposed bail package is insufficient to reasonably to assure his appearance as required," according to ABC.

Judge Amy Berman Jackson placed a gag order on the trial and warned both sides not to "try the case on the courthouse steps."

"This is a criminal trial, not a public relations campaign," Jackson said.

Prosecutors said if the op-ed had been published it would have violated the judge's order because it was written "to influence the public's opinion of defendant Manafort, or else there would be no reason to seek its publication — much less for Manafort and his long-time associate to ghostwrite it in another's name."

The former campaign chairman was indicted in October as part of the ongoing Russia probe on 12 counts related to work done before joining the Trump campaign, including conspiracy against the U.S., conspiracy to launder money and serving as an unregistered agent of a foreign principal. Manafort pleaded not guilty to all the charges.